This invention relates to a method and an apparatus for preventing pulsations in a fluid being transported to flow from a sending or flowing-out section under pressure to a point of destination through a piping system. More particularly, it relates to a method and an apparatus for preventing pulsations in a flowing fluid when the latter is transported under pressure by a diaphragm pump, plunger pump or a gear pump liable to produce pulsations in the flowing fluid.
In general, when transporting liquids or gases such as solvents, paints or photosensitive coating liquids under pressure to another device or equipment through a piping system, pumps liable to produce pulsations, such as diaphragm pumps, plunger pumps or gear pumps, are frequently employed.
However, in case vigorous pulsations occur in the flowing fluid being forcibly caused to flow under pressure, the fluid is transported and supplied only intermittently, so that it becomes difficult to transport and supply the fluid at a constant flow rate. In addition, the pumps may be subjected to an overload due to pressure fluctuations caused by pulsations, resulting frequently in the troubles caused to the pumps.
Also, when transporting a photosensitive coating liquid to a coating apparatus for coating, uniform coating cannot be obtained in case pulsations occur in the photosensitive coating liquid during transport thereof under pressure, so that the coated products cannot be used effectively as the photosensitive material. In addition, in the case of the coating process employing paints or the like coating compositions, the latter may be discharged unevenly or interruptedly, so that it is extremely difficult to achieve uniform coating.
Therefore, when transporting the liquid under pressure through a piping system by a pump, it is necessary to reduce the liquid pulsations to as small a value as possible.
For preventing or reducing the aforementioned pulsations caused during liquid transport under an elevated pressure, a typical conventional practice has been to provide a hermetically closed hollow chamber in communication with a portion of a conduit pipe extending from a pumping section, such as a pump, to a point of destination, in such a manner that the pulsations caused during the transport flow under an elevated pressure will be absorbed by compression and expansion of the air occurring in the hollow chamber. The internal space of the hollow chamber is hermetically sealed from the ambient atmosphere provided that it is kept in communication with the conduit pipe, with the air pressure therein having been equal to the atmospheric pressure prior to starting of the liquid transport under the elevated pressure. Since the liquid intrudes under pressure into the hollow chamber during the transport flow, the air pressure in the hollow chamber is raised to a value higher than the atmospheric pressure.
The Japanese Patent Kokai Publications Nos. 56(1981)-160497 and 58(1983)-217890 and the Japanese Utility Model Kokai Publication No. 59(1984)-73692 are directed to the methods and apparatus pertinent to the present invention.